Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-05-10
2001-03-27
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C528S123000, C562S887000
Reexamination Certificate
active
06207733
ABSTRACT:
RELATED APPLICATIONS
This application claims priority to Austrian Application No. A 802/98, filed May 12, 1998, herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
Water-dilutable two-component epoxy resin systems which cure at room temperature have reached a technological level which comes close to conventional epoxy resin systems with respect to the desired properties such as adhesion to substrate, surface quality, and mechanical and chemical resistance.
Attempts were made, for convenience and processing safety, to develop monocomponent (1C) epoxy resin systems with latent catalysis, consisting of a combination of ketimines and epoxy resins. The advantages of these 1C systems are obvious: the hardener and epoxy resin are already present in the proper proportions, so that there is no danger of using an incorrect proportion. In conventional systems, curing occurs when the ketimines are hydrolyzed by moisture from the air. With water-dilutable systems, it is preferable to add a definite quantity of water, so that the curing time no longer depends on the humidity. Moreover, this leads to homogeneous curing through the entire film thickness, thereby improving the properties of the cured resin.
2. Description of the Related Art
Conventional 1C systems have been known for a long time, and are described in the following patents, for example: U.S. Pat. Nos. 3,442,856, 3,919,317, 4,148,950, 4,391,958, 4,748,083 and WO Application 92/18575.
Water-dilutable 1C systems with latent catalysis are described in WO-A 98/02478. A water-dilutable liquid epoxy resin is combined with ketone-blocked amines, known as ketimines. When water is added, the ketimine decomposes and the amine hardener is regenerated and is available for curing. As the system can be emulsified in water, this is an aqueous binder, the properties and processing of which are known to users of the two-component aqueous systems. This binder assures easier processing for the user, as the binder is already present at the correct ratio of hardener to epoxy resin. The curing reaction is started by addition of water, so that only a minimum quantity of water need be added to attain optimum properties for the coating.
Suitable amines which react with ketones to give ketimines include aliphatic linear, branched or cyclic amines with at least two primary amine groups, primary polyoxyalkylene diamines, partially or completely hydrogenated condensation products of aniline or its derivatives, as well as polyamidoamines with at least two terminal primary amino groups from aliphatic linear, branched or cyclic amines with at least two primary amino groups and dicarboxylic acids.
These amines have disadvantages, though. For instance, low molar mass diprimary amines combined with water-dilutable epoxy resins hardly give the desired properties such as good surface quality and a balanced ratio of film hardness to film flexibility after curing. Although polyoxyalkylene diamines are of high molar mass, their aliphatic and polar nature produces insufficiently water-resistant films. Condensation products of aniline derivatives, even if completely hydrogenated, are not very reactive at ambient temperature, which means that the curing time is long.
Non-hydrogenated, or only partially hydrogenated, products are also toxicologically objectionable. Amine hardeners for ketimine capping should contain solely primary amino groups, because only those can react easily with ketones, with elimination of water. Reaction of secondary amines with ketones to give enamines proceeds less smoothly. A residue of unblocked amines remains, seriously degrading the storage stability of the 1C systems. For that reason, epoxide-amine adducts and Mannich bases are not very suitable for ketimine capping.
Polyamidoamines meet the requirement that they contain only primary amino groups, and they also have the desired polymeric structure. One disadvantage of the less polar polyamidoamines is their poor compatibility with the water-dilutable epoxy resins. That is particularly the case if the dicarboxylic acids used have long chains (10 or more carbon atoms in the chain). Polyamidoamines based on short-chain dicarboxylic acids, on the other hand, are often crystalline and high-melting, and thus difficult to work with.
Poor compatibility of ketimines based on polyamidoamines with water-dilutable systems becomes apparent to the user primarily through surface problems and cloudiness in unpigmented paint films in the cured systems. The problem can, indeed, be reduced by adding suitable solvents; but that impairs the solvent balance of the system. Also, the advantages of an aqueous 1C system are partially lost.
OBJECT OF THE INVENTION
Now it has been found that an amine hardener suitable for ketimine capping, which combines in an ideal manner a high molar mass structure and good compatibility with water-dilutable epoxy resins, can be produced in a simple manner. That is done, in the first step, by reacting amine A, having at least two primary amino groups, in proper proportions with a cyclic alkylene carbonate B, preferably an &agr;,&ohgr;-alkylene carbonate, to produce hydroxyalkyl urethanes AB. Then the remaining primary amino groups are reacted with aliphatic carbonyl compounds C to give ketimines ABC. In the subsequent step, at least two molecules of this precursor are mixed, through the preferably primary OH groups formed in the reaction with alkylene carbonate, with suitable multifunctional OH-reactive compounds D.
SUMMARY OF THE INVENTION
The present invention is therefore related to capped amine hardeners for epoxy resins, which are reaction products of amines A having at least two primary amino groups, cyclic alkylene carbonates B, aliphatic carbonyl compounds C and compounds D having at least two groups which react with hydroxyl groups. In the first step, for each 1 mol of amine A, 0.1 to 1 mol of the primary amino groups are converted, by reaction with the cyclic alkylene carbonate B, to hydroxyalkyl urethane groups. The remaining primary amino groups react in the second step with the aliphatic carbonyl compound C to give ketimine or aldimine groups. Then, in the third step, at least two of the molecules formed from A, B and C are linked with compound D through reaction of the hydroxyl groups of the hydroxyalkyl urethanes with compound D.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The amines A are selected from aliphatic linear, branched and cyclic, and mixed aliphatic-aromatic amines having at least two primary amino groups. Diamines are preferred, and diamines with no other secondary amino groups are particularly preferred. Examples of particularly suitable amines are: ethylene diamine, 2,2,4- and 2,4,4-trimethylhexamethylene diamine, neopentane diamine, 2-methyl-1,5-pentane diamine, 1,3-diaminopentane, hexamethylene diamine, and cycloaliphatic amines such as 1,2- or 1,3 -diaminocyclohexane, 1,4-diamino-3,6-dimethylcyclohexane, 1,2-diamino-4-ethylcyclohexane, 1,4-diamino-3,6-diethyl-cyclohexane, 1-cyclohexyl-3,4-diaminocyclohexane, isophorone diamine, and their reaction products, bis-(4-aminocyclohexyl)-methane, bis-(4-aminocyclohexyl)-propane, 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane, 1,3- and 1,4-bis-(aminomethyl)-cyclohexane, and aromatic amines with aliphatically bound amino groups such as 1,3- and 1,4-bis(aminomethyl)benzene. Of these, ethylene diamine, hexamethylene diamine, 1,2-diaminocyclohexane, isophorone diamine, bis-(4-aminocyclohexyl)-methane and 1,2-bis-(aminomethyl)benzene (m-xylylene diamine) are particularly preferred.
The cyclic alkylene carbonates, B, are esters of the carbonic acid with aliphatic diols, such as 2-keto-1,3-dioxolane, which may be substituted in the 4 and 5 positions by alkyl groups with, particularly, 1 to 4 carbon atoms; 2-keto-1,3-dioxane and 2-keto-1,3-dioxepane, which likewise may be substituted on at least one of the ring carbon atoms. Particularly suitable compounds are cyclic carbonates derived from diols such as ethylene glycol, 1,3-propylene glycol or 1,2-propylene glycol, and 1,
Feola Roland
Gmoser Johann
Mueller Friedrich
Aylward D.
Dawson Robert
Frommer & Lawrence & Haug LLP
Vianova Resins AG
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